Paving machine for forming porous pavement construction

ABSTRACT

A paving machine forms aqueduct channels using a screed assembly having elongated forming arms, and deposits pavement material onto these arms. As the machine advances, channels are formed in the pavement layer. This results in a porous pavement material having a number of aqueduct channels formed underneath the pavement surface, so that water can percolate downward into the pavement and enter the channels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to pavement material, pavement construction, andboth devices and methods for forming such pavement material and pavementconstructions. More particularly, this invention concerns the recyclingof asphalt and concrete, and the construction of environmentally soundand safe roads.

2. Description of the Related Art

FIG. 1 is a cross-section of a region of a conventional asphaltpavement. Large aggregate 1 is mixed with small aggregate (or sand) 2,and these components are bound by tar 3. The top of the asphalt pavement4 is exposed to traffic, while the bottom of the asphalt pavement restson existing sub-base soil 5.

The top of the asphalt pavement 4 is exposed to the elements, and so issubjected to ultraviolet light from the sun, rain, snow, freezing duringwinter and thaw during spring. The pavement also experiences frictionalwear due to vehicular traffic thereon.

Over time, these environmental and service factors cause the asphaltpavement to deteriorate. As a result, particles of asphalt 4, largeaggregate 1, and small aggregate or sand 2 coated with tar 3 may beswept into drainage systems such as pipes and storm inlets. Thesedrainage systems typically discharge into lakes, rivers, streams oroceans. As will be explained hereafter, such pavement particlescontribute to water pollution.

The specific gravity of the tar particles 3 is very close to that ofwater, which has a specific gravity of one. Accordingly, when rainwater,sleet, and melting snow drain from the asphalt pavement, the tarparticles 3 float and are swept into the bodies of water, such as lakes,rivers, streams and oceans, which receive the water discharge.

Tar particles 3 that are attached to small aggregates such as sand 2 areusually carried off into drainage systems such as pipes, culverts andstorm inlets, where they settle to the bottom, since the tar andaggregate together have a specific gravity greater than that of thewater.

Over time, as the asphalt pavement continues to deteriorate, aconsiderable quantity of aggregates 1 and 2 coated with tar 3accumulates at the bottom of bodies of water, thereby depleting theoxygen in the water, and reducing the amount of aquatic life. Inaddition, the tar may contain heavy metals, which have already beenshown to have other adverse effects. The results of such pollution arewell-known, and it can markedly affect the health of wildlife andhumans.

The continued degradation of asphalt pavement often results inpot-holes, which are major structural failures of the asphalt pavement.Asphalt material breaking away from these potholes also causesaccelerated pollution of water resources in the manner alreadydiscussed.

A substantial amount of the water pollution which enters ground water,whether in aquifers, streams, rivers, bays or oceans, thereforeoriginates as runoff from asphalt and concrete roads and parking lots.Wherever there are asphalt or concrete roads, driveways, or parkinglots, pavement-based pollutants are likely to be introduced into thewater runoff.

These water pollutants include hydrocarbons, which are inherentlypresent in asphalt pavement. Asphalt pavement is composed of tar, sandand rock aggregates. The tar component of an asphalt road functions as abinder which holds the aggregate particles together. Tar is athermo-plastic material, and it deteriorates when exposed to heat and/orultraviolet energy. Since any asphalt used outside is continuallyexposed to heat and ultraviolet energy from the sun, that asphalteventually degrades. Furthermore, vehicle traffic also wears down theasphalt road surface. As a result of both the thermal/ultravioletdegradation and physical wear, components of the asphalt road arereleased. As previously explained, these components are carried by stormwater runoff into roadside waters and ditches which lead throughstormwater systems to large bodies of water such as lakes, rivers, baysor oceans, and from there, into drinking water aquifers.

Still other sources of pavement degradation are the freeze-thaw cyclesexperienced during winter seasons, and the pumping action produced byvehicle traffic. Both of these phenomena physically flex the roadwaysand so cause pavement degradation, which further undermines both asphaltand concrete pavement.

Both asphalt and concrete roads also contain oil drippings which havefallen from passing vehicles. These oil drippings, which are eventuallyflushed into water outfalls, are a further source of water pollution.

Thus, tars, pavement particles, and vehicular oil drippings, whether onasphalt or concrete pavement, all of which are polluting substances, arecarried into stormwater systems such as sewers, ditches, culverts, etc.,from where they are ultimately deposited into streams, lakes, rivers,bays and oceans, so that they can enter the drinking water or foodsupplies. Using retention ponds to store stormwater is of no benefit;such ponds grow polluted and they become another source of ground waterpolluted by hydrocarbons and heavy metals.

It has been determined that hydrocarbon pollutants entering the watersupply create serious health problems for both humans and wildlife. Suchhydrocarbons are particularly detrimental when they enter the drinkingwater supply, since many water treatment plants add chorine to the waterto kill bacteria. Chlorination of the drinking water creates conditionswhich lead to the production of chlorinated hydrocarbons. Chlorinatedhydrocarbons are carcinogenic, so the presence of such cancer-causingchemicals is clearly undesirable.

Water treatment plants are not usually equipped to remove hydrocarbons,sulfur or dissolved metals from drinking water. Accordingly, byeliminating or at least reducing the amount of hydrocarbons, sulfur andheavy metals emanating from asphalt roads, adverse effects on drinkingwater can be reduced.

Still another reason why asphalt roads contribute to water pollution isbecause road tar contains heavy and light metals and sulfur. Heavymetals (i.e., copper, lead and mercury) and light metals (i.e., aluminumand arsenic) have been shown to be detrimental to the health of man andwildlife, especially if they enter the food chain. Sulfur, when combinedwith rainwater, acidifies the water, and the acidic runoff in turnacidifies lakes, rivers, streams, bays and even oceans. While thepresence of such acids in water has been attributed to acid carryingclouds, which produce "acid rain," asphalt roads also contain sulfurwhich can be flushed out and contribute to acidic runoff. This acidicrunoff, flushed from parking lots, streets and highways, is anothersource of acid water, which is perceived as the phenomenon "acid rain".

It is therefore essential that the tar in asphalt roads be renderedenvironmentally safe as a binding element. One way to do this would beto recycle the road material into an environmental non-polluting porouspavement.

Even non-polluting water runoff can be troublesome, because of theflooding which can result. This is a particular concern innewly-developed areas, where the construction of residential andbusiness sub-divisions, shopping centers and roads may lead to increasedwater runoff. If the runoff exceeds the area's drainage capacity,flooding can occur.

A further concern in the design of roadways is the need to avoid havingstanding water on the roadway. It has been determined that the majorityof skidding accidents occur because water has accumulated on theroadway. When a vehicle passes over such standing water, the water mayaccumulate under one or more of the vehicle's tires. This causeshydroplaning, which is a situation where the vehicle tire loses contactwith the road surface, and "floats" on a film of water. Needless to say,hydroplaning is quite dangerous, since the ensuing skidding can cause aloss of control.

Thus, there is a substantial need to provide roads which do not allowstanding water to form thereon.

Still another concern in designing roads arises because conventionalasphalt and concrete roads are composed of stone aggregates and sandwhich become polished by vehicle traffic. This polishing reduces thecoefficient of friction between vehicles tires and the road, makingskidding more likely.

Moreover, asphalt roads contain oils, which further reduces thecoefficient of friction between tires and the asphalt roadbed. Inaddition, oil drippings which accumulate on the surface of eitherasphalt or concrete roads also can cause skidding.

Accordingly, it is highly desirable to provide roads in which there is ahigh coefficient of friction between the road surface and the tires ofpassing vehicles.

Another aspect of this invention relates to improving the types oftrucks which are used to process road paving material as it is shippedto the location where it will be formed into pavement. Conventional bulkmixing machines, which are known as transit mix trucks, are designed tomix conventional concrete. These machines are designed to mix relativelyhigh slump materials, high meaning slumps ranging from 1-4. Lower slumpsof concrete, i.e., concrete containing lower water-cement ratios, aredifficult to produce using transit mix trucks, since such trucks containangularly positioned rotatable drums with fixed internal blades that mixthe concrete as it flows over the blades of the rotating drums. If onetries to produce low slump low moisture concrete in these machines, oneends up producing inhomogenous balls of concrete which have undergonelittle or no mixing. Furthermore, transit mix trucks are not designed tohandle polymeric admixtures, as described throughout this application.Since such admixtures would render the mixing machines "sticky", theaddition of such admixtures would cause cement to adhere to the insidesurface of the truck's drum, rendering it virtually impossible to clean,and possibly even damaging the transit-mix truck.

Another conventional concrete mixing machine is known as a mobile mixer.Mobile mixers carry dry sand, stone aggregates, water and admixtures inseparate compartments which are arranged on a truck bed. When the mobilemixer arrives at a construction site, the materials are batchedmechanically, usually through a series of gates and valves. Mixing isperformed by a mixing augur provided at the rear of the machine. Onedisadvantage to using these mobile mixers is that the augur must rotatecontinuously, and can never stop during processing, because the augurmust rotate in order to achieve a homogenous mix. This, however, isnearly impossible to achieve, since whenever the machine is moved todifferent job sites, the augur must be stopped so that concrete will notpour out from the truck during relocation. Accordingly, the mobilemixer, while superior to the transit mix truck for batching low slumpmixes, nevertheless suffers from the same disadvantages that werediscussed previously with regard to the mobile mixers, namely, when themachine is stopped for transport, dry and non-homogenous concreteresults.

While there are other types of mixing machines commercially available onthe market, such machines are of quite limited mobility, or theyotherwise suffer from at least some of the shortcomings of the transitmix truck and/or the mobile mixer.

Still another disadvantage of both the transit mix truck and the mobilemixer is that, once they have run out of concrete, they usually must bereturned to a batch plant to be replenished with a fresh supply ofmaterial. These machines are therefore not well-suited for on-sitebatching and mixing.

Furthermore, the batching and mixing of recycled asphaltic products("RAP") are not easily accomplished using currently available equipment.

SUMMARY OF THE INVENTION

In contrast to the prior art, the invention of recycled environmentalporous pavement reverses the pollution cycle caused by asphalt roads andconverting the hydrocarbons and tar polluting constituents intoenvironmentally safe material and constructing a recycled porouspavement, which helps to control stormwater runoff and flooding, therebygreatly reducing pollution to waterways.

One aspect of the present invention involves recycled environmentalporous pavement, which is constructed by converting otherwise pollutingasphalt or concrete pavement into a non-polluting recycled environmentalporous pavement. The porous pavement allows water to pass through it ata high rate, and so it reduces water pollution which would otherwiseoccur because of runoff from asphalt and concrete roads. The porouspavement also reduces flooding, and since it allows water to passthrough to the sub-soil, it facilitates recharging ground water-tablesand aquifers. Because there is so little stormwater runoff, pollution ofstreams, lakes, rivers and oceans is greatly reduced.

It is especially desirable that tars used as binding agents in asphaltroads be rendered environmentally safe. This invention does so byrecycling asphalt roads into non-polluting porous pavement.

One aspect of the present discovery, recycled environmental porouspavement, reverses the pollution cycle by recycling existing pollutingasphalt and concrete roads and other polluting materials into chemicallysafe and non-polluting paving materials. By recycling asphalt andconcrete roads into non-polluting porous pavement, both water runoff andpollution can be virtually eliminated.

This invention includes the basic novel disclosure of the constituentsof recycled environmental porous pavement.

An aspect of this invention extends to a paving machine for formingpavement as the paving machine moves along a direction of travel. Thepaving machine may include a mixing unit having a hopper and at least apair of mixing rolls disposed therein for processing pavement material,and a screed for depositing pavement material onto the subsurface. Thescreed has elongated forming arms each having a cross-sectional shapeand which forming arms are approximately parallel to one another, and tothe direction of travel. The screed deposits the pavement material ontothe arms so that as the paving machine advances, the pavement is formedwith a plurality of channels therein. A conveying means conveys thepavement material from the mixing unit to the screed. Differentcross-sectional shapes can be used, and the forming arms may be tapered,or can rotate about a rotation axis approximately parallel to thedirection of travel. A smoothing roll can be located by the screed, andthis roll has an axis approximately perpendicular to the direction oftravel.

In addition, paving machines can be improved by providing applying meansfor applying treating agent to the pavement, for example, in the form ofa reservoir for containing treating agent, a nozzle for applying thetreating agent to the pavement, and a pump that feeds the treating agentfrom the reservoir to the nozzle. Such fogging spray nozzles can belocated beyond the rollers to coat the finished pavement with curingcompound. The fogging spray nozzles coat the finished pavement withcuring compound, and the fogging spray can be adjusted at the nozzle andpump to ensure a fine mist spray.

The curing compound serves to control and reduce the evaporation rate ofthe pavement material using its hydration or curing process. There aremany commercially available curing compounds available on the market.They are basically liquid plastics such as liquid acrylics, liquid latexand other polymers.

Still another aspect of this invention is the formation of a pavementconstruction having a layer of porous pavement material with channelsformed beneath its surface. The pavement is made from pavementparticles, and the layer of pavement particles has voids at least someof which are disposed between adjacent pavement particles, allowingwater to drain therethrough. In some cases, the channels can besubstantially parallel to one another, and may have round or rectangularcross-sections. Materials such as porous concrete can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a conventional section of asphaltpavement.

FIG. 2 is a cross-sectional view of porous pavement according to thepresent invention.

FIG. 3 is an enlarged cross-sectional view of the pavement shown in FIG.2.

FIG. 4A is a perspective view showing a roadbed constructed according tothe present invention; FIG. 4B is a front cross-sectional view of theroadbed depicted in FIG. 4A.

FIG. 5 is a cross-sectional view of an overlayment according to thepresent invention used with a pre-existing roadbed.

FIG. 6 is a cross-sectional view of a roadbed made from porous pavementaccording to the present invention.

FIG. 7 is a cross-sectional view showing a roadbed made from porouspavement according to the present invention having an aqueduct structureaccording to the present invention.

FIG. 8A is a side elevational view of a paving machine for producingpavement according to the present invention.

FIG. 8B is a rear elevational view of the paving machine shown in FIG.8A.

FIG. 8C is a perspective view of the portion of the screed assembly ofthe paving machine shown in FIG. 8A which produces an aqueduct structurein pavement.

FIG. 8D is a rear elevational view of portion of the screed assemblyshown in FIG. 8C.

FIG. 9A is a cross-sectional view of a porous rubber overlaymentfriction course, and FIG. 9B is a perspective view of the overlaymentfriction course of FIG. 9A. FIG. 9C an embodiment of the rubberoverlayment friction course containing grooves on its underside.

FIG. 10A is a side elevational view of a mixing machine in accordancewith this invention. FIG. 10B is a front cross-sectional view of amixing machine as seen along lines 10B--10B of FIG. 10A, FIG. 10C is atop view of the spray head shown in FIG. 10A, FIG. 10D is an enlargedschematic view of the spray head with its cover removed, and FIG. 10E isa side view of the spray head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 depicts environmental porous pavement which can be produced inpart by recycling pre-existing and otherwise polluting asphalt pavement.Alternatively, this pavement could be made using fresh asphalt, or evenother materials, such as crushed recycled concrete, crushed stoneaggregates and sand, crushed brick, crushed concrete masonry units, etc.

Each particle of pavement material consists of an inner core ofaggregate 6 and an encapsulating outer shell 6' made from non-pollutingcement. The inner aggregate core 6 is itself coated with recycledasphalt (fresh asphalt or other material also could be used). Thepavement has a thickness T and is formed atop the existing sub-base soil5.

FIG. 3 shows an enlarged cross-sectional view of the environmentallynon-polluting porous pavement which can be made from recycled asphaltpavement. Here, the aggregate core 6 consists of particles of aggregate1, typically limerock, granite, or other hard stone, and sand 2, whichare surrounded by an asphalt coating 3. This asphalt coating 3 envelopesthe aggregate 1 and/or sand 2 (either partial or total coverage ispossible). Although this asphalt is ordinarily a significant source ofpollution in conventional asphalt roads, this pollution is prevented bythe following aspects of this invention. Incidentally, existing federal,state and county roads, all of which contribute greatly to pollution,all contain the optimum size of aggregate materials, which is 3/8" insize or smaller. In any event, the size of the aggregate used in suchexisting roads is set forth in existing road standards.

A cementitious coating 6' composed of non-polluting cement, which isthermosetting, encapsulates the otherwise-polluting asphalt coating 3.Because the encapsulating coating 6' is thermosetting material, thisensures that the polluting asphalt element 3 is forever isolated, sincethermosetting material does not soften in the sun or deteriorate fromultraviolet energy. Thus, the cementitious encapsulating coating 6'renders the pavement environmentally safe. An example of a typicalcementitious coating is Portland cement, which is commercially availablein the field of construction. In this regard, types I, II and IIIPortland cements are suitable for use with this invention and are allcommercially available.

The recycled environmental porous pavement contains voids 8 throughwhich water from rain or melted snow percolates, as shown in FIGS. 2 and3. It is the presence of these voids which makes the pavement porous,and so it will be appreciated that the size and number of voids can beselected to provide the pavement with a particular porosity. Moreover,the subsequent discussion of mixing machines in the following portionsof this application addresses the properties of asphalt, such asdensity, coating thickness, viscosity, etc. Testing has shown that amaximum of 44% voids is possible. The average percent voids is 27%. Thevoids are the result of the mix design that has been discussed and theresult of the forming process.

An optional second coating sealant 7, shown in FIG. 3, which can be anon-polluting coating absorbed by the cementitious coating 6', may beprovided to surround the individual pavement particles. This secondcoating 7 alters the flexural properties of the cementitious coating 6'.The second coating sealant 7 also serves to produce a secondencapsulating seal, supplementing the seal formed by the cementitiouscoating 6'. Thus, there is added encapsulation and sealing of theexisting asphalt coating 3 which at least partially surrounds theaggregates 1 and sand 2.

Examples of materials which can be used for the second environmentalcoating sealant 7 include families of polymeric admixtures such asliquid or powder which are water-based, non-polluting, and arecommercially available in the construction field as liquid or powderacrylics or liquid or powder latex. Other commercially available liquidadmixtures, specifically non-polluting, may also be used, and can bespecified for a particular design.

This invention encompasses a wide variety of paving materialcompositions. The following examples of different pavement constructionsare merely illustrative, and this invention should not be construed asbeing limited to such constructions.

The following mixing ratios are based upon volumetric measurements, notweight. This is due to the fact that the percentage of voids required inthe porous pavement according to this invention is itself volumetric innature. Boring and lab tests are used to determine the percentage ofasphalt and the degree of encapsulation.

To determine the volumetric ratios which must be regulated, the mixingassembly 203 is calibrated based upon volumetric capacity.

EXAMPLE 1

If the mixing assembly contains 4.5 cubic yards (3.4 cubic meters) ofmaterial, a solid 1:2:4 mix design would contain 1 part of cement, 2parts of sand, and 4 parts of aggregate or recycled asphaltic material(RAP). Thus, the total volumetric value for the solid mix design is1+2+4=7 parts. ##EQU1##

EXAMPLE 2

Porous pavement can be obtained by altering the mix used in Example 1 todecrease the 2 parts of sand to just 1 part of sand. Thus, the mixdesign for the porous pavement would be 1:1:4, that is 1 part cement, 1part sand, and 4 parts of aggregate or recycled asphaltic product (RAP).The total volumetric value of the environmental mix design according tothis example of the invention is 1+1+4=6 parts, and so the percentporosity is: ##EQU2## By eliminating sand altogether, and providing amix composition of 1+0+4 (cement:sand:aggregate)=5 parts, ##EQU3##

EXAMPLE 3

Another embodiment of the pavement material according to this inventionis as follows (the ratios given are volumetric ratios):

1 part of cementitious coating to 3 parts of aggregates coated with tar;

1 part of sand coated with tar; and

1/10 part of the second coating sealant.

EXAMPLE 4

Yet another example of pavement material employing these increasedamounts of cementitious coating 6 and second coating sealant 7 is:

11/2 parts of cementitious coating by volume;

3 parts of aggregates coated with tar by volume;

1 part of sand coated with tar by volume; and

1/5 part of second coating sealant by volume.

It has been determined that the volume of admixture added to the waterdoes not affect the porosity of the mix design. The admixture serves toproduce the sealing and encapsulating qualities of the cementitiousmaterial 6 and coating sealant 7.

The suggested starting formulation for the admixture is based upon thedegree of encapsulation of asphalt which is desired. When there is ahigh percentage of asphalt, say, 10%, encapsulating the aggregates(RAP), a high ratio of admixture to cement should be used, such as 20%by weight of the admixture to the weight of the cement. These highratios of asphaltic coatings of RAP are typical of newly-paved asphaltroads.

As an asphalt road ages, say over a period of five years (an acceptedlifespan for an asphalt road, after which it will require resurfacing),the road's hydrocarbon content is substantially reduced. This reductionis caused by environmental factors such as the ultraviolet light fromthe sun, rainwater, freeze-thaw cycles during a winter period, de-icingchemicals such as salt spray, road wear by vehicular traffic, and theevaporation of volatile hydrocarbon components from the asphalt as thepavement ages.

It is expected that asphalt content will diminish by 2-3%. Accordingly,the preferred ratio of the admixture to cement for these older roads is10%.

The ratio of water to cement for pavement having a high content ofrecycled asphalt product (RAP) is 35% by weight.

The ratio of water to cement for roads having a low content of recycledasphalt product is 40% by weight.

The volumetric proportions of the cementitious coating 6 and the secondcoating sealant 7 can be increased depending upon the amount of asphalt3 coating the aggregate 1 and sand 2. The amount of asphalt 3 may beselected using standard laboratory testing procedures, such as "SamplingAsphalt Products for Specifications Compliance" (MS-18) AASHTO (AmericanAssociation of State Highway and Transportation Officials) Method oftest T40 and ASTM Method of TEST ?140.

Although a wide variety of materials can be used in practicing thisinvention, the following discussion of various exemplary constituents ofenvironmental pavements may be of interest.

It is preferable that the admixtures used to form pavement materials andpavement constructions according to this invention be liquid, have asolid content of acrylic about 47% by weight. The balance of theadmixture is water, and the admixture has a pH of 9.3-10.2, specificgravity of 1.059, and an absolute viscosity of about 1.5dynes-seconds/100 cm².

It is preferable to use sand or fine aggregate of the type set forth inthe following table

    ______________________________________                                        Sand or Fine Aggregate                                                        Sieve Size          Percent Passing                                           ______________________________________                                        #4                   0-5                                                      #8                   0-15                                                     #16                  3-35                                                     #30                 30-75                                                     #50                 65-95                                                     #100                93-100                                                    ______________________________________                                    

The fine aggregate (sand) should be reasonably well-graded from courseto fine and when tested by means of laboratory sieves, it should meetthe above-requirements, in percent of total weight.

It is also believed to be preferable to use aggregate having as narrow asize distribution as possible--in other words, all of the aggregateparticles should be of the same size. #30 size material is thought to bepreferred. This observation was made during development of thisinvention, wherein it was discovered that porosity could be maximized bymaking all of the pavement particles the same size. Likewise, it isthought to be preferable for the aggregate particles to be as close tospherical in shape as is possible.

So too, it is thought that the preferred asphaltic material to be usedwith this invention is AC-5 Grade Asphalt Cement (contained in RAP),having a viscosity at 140° F. (60° C.) of 500 poise, a viscosity at 275°F. (135° C.) of 175 Cs and a measured penetration at 77° F. (25° C.) for100 gms over a 5 second period of 140. The flash point (COC°) of thismaterial is 350° F. and its solubility in trichloroethylene is 99.0%.

Moreover, it is preferred that the Portland cement used with thisinvention be any of types I, II or III, as specified in AASHO M 85, ortype IS, as specified in AASHO M 151.

The water to be used in preparing the paving material should come fromapproved municipal water supplies. Water from other sources should betested and confirmed suitable before use, and it should not containimpurities in excess of the following limits: acidity should be no morethan 0.05%, the total amount of organic solids not be more than 0.05%,the total amount of inorganic solids be less than 0.08%, and the totalamount of chloride or sodium chloride be less than 0.05%.

The size of the large aggregates, including recycled asphaltic products(RAP), should be 3/8" (9.52 mm)±10%, for screened material. Smalleraggregates produce a lower coefficient of friction and larger aggregatesproduce a higher coefficient of friction, although this also results ingreater road noise. Again, it is believed to be preferable for theaggregates to be selected so as to have as narrow a size distribution aspossible, and to be as close to spherical in shape as possible.

It should be noted that the sand 2 and stone aggregate 1, both of whichhave asphalt coatings 3, as shown in FIG. 3, can be produced by milling,crushing and screening of existing polluting roadway material, forexample, roadbeds. Alternatively, fresh raw material could be used. Thiscan be done using commercially available milling, crushing, andscreening equipment. A wide variety of milling, crushing and screeningmachines are known, and which perform with varying degrees of automationand control. Thus, applicability and control of a particular piece ofequipment for milling, crushing and screening of recycled asphaltmaterial can be determined by the nature of the recycling project andthe degree of automation desired. This invention does not require theuse of any specific piece of processing or construction equipment, andall devices are intended to fall within its scope.

The inventors have found that using prior art devices, such as transitmix trucks, mobile mixers, and other similar types of commerciallyavailable equipment, poor results were obtained in the mixing operation.These devices produced non-homogenous mixes, and created the problemsthat have been described previously. The mixer described in thisapplication can produce conventional concrete as well as porous pavementmaterial according to the invention described herein. Even using thismixer to produce conventional concrete will be beneficial because thatconventional concrete will be produced with greater homogeneity.

Accordingly, this invention also includes a mixing machine for use inmanufacturing the homogenous environmental porous pavement materialpreviously described. This machines is depicted in FIGS. 10A-E, and isdescribed hereinafter.

A mixing machine for use in practicing this invention is shown in theelevational view of FIG. 10A. This mixing machine is especially usefulfor producing porous pavement materials, such as those of the typedescribed in U.S. Pat. No. 3,870,422 to Medico, Jr.

The mixing machine proposed in this invention is particularly useful formixing environmental porous pavement, since this machine allows precisecontrol of the admixture, water and cement ratios, as well as precisecontrol over the volume of the admixture, water and cement, which formthe cement coating of the asphalt covered aggregate (RAP), and which hasbeen described previously.

As shown in FIG. 10A, Portland cement flows through hose 200, which hoseis attached by clamping or screw coupling 201d to the spray headassembly 201, and is located atop the cementitious mixing assembly 202.As shown in FIG. 10B, the mixing assembly 202 has paddles 202a to churnthe material being mixed. These two assemblies, 201 and 202respectively, are attached to the top of the large mixing assembly 203,which is loaded with aggregates, sand and gravel 204, collectively, orwith recycled asphaltic product (RAP). The large mixing assembly 203 isloaded by means of material handling equipment 205, such as frontloaders, conveyor belts, batching silos or any other suitable materialshandling equipment, both of the types now known, and any types which maybe developed hereafter. The cement 208 is loaded by means of the base200 into the mixing assembly 202. The water 206 and the admixture 207combine in the ring pipe 201a.

When the contents of the mixing assembly 202, sand and aggregate 204,are mixed with water 206, admixture 207, and cement 208, they formcementitious coatings 6 and 6', respectively, which combine to formenvironmental porous pavement material 209. The mixing of the cement 208with the water 206 and admixture 207 takes place within the mixingassembly 202, and forms the cementitious coating 6, as shown in FIG. 3.

This cementitious coating 6' drops down into the large mixing assembly203 where it combines with sand and aggregate during the mixingoperation. This mixing operation, which is performed by counter-rotatingpaddles 203a, causes the cementitious coating 6' to encapsulate theaggregate, sand and gravel 204, or the recycled asphaltic product (RAP).

This RAP material contains completely covered asphalt or partiallycoated asphalt that was previously coated at the asphalt plant.

If desired, particles of aggregates composed of ordinarily pollutingasphalt could be used alone in the mixing operation just described, andthose aggregate particles would be encapsulated with the cementitiouscoating 6', thereby rendering it environmentally safe.

An optional second coating sealant 7 may be provided when the completedmixture is still in the large mixing assembly 203, for example, by meansof the spray head assembly 201.

The environmental porous pavement material is fed to pump 210, and inturn, through tubes 210a, which deliver the material 209 to the pavingmachine 101. Although it is preferable for this paving machine to be thepaving machine described elsewhere in this disclosure, and depicted inFIGS. 8A and 8B, other paving machines also could be used, includingconventional devices.

The mixing machine in FIG. 10A is driven by operator 211, who has aclear view of the loading and mixing operations through the window 211a.The operator sits on a pedestal seat 212, which can be swivelled andotherwise positioned so that the operator can control the mixing machinewith ease as it moves to desired locations. The mixing machine can bepowered by engine 213, which drives hydraulic system 214,counter-rotating paddles 203a, and pump 210. The self-propelled mixingmachine rides upon wheels 215, but of course could instead ride upontreads. 10B depicts the counter-rotating paddles 202a in thecementitious mixing assembly 202 which can be driven by chain drive orpulley 225, which cooperates with drive wheels 215 and the hydrauliccylinders which control the supporting cable 217 of tube 210.

Homogenous mixing of pavement material starts at the spray head assembly201 where cement 208, such as Portland cement, enters through hose 200under pressure from a supply tank and blower, which are themselveswell-known and commercially available, and so are not shown. As thecement 208 enters the spray head assembly 201, water 206 enters ringpipe 201a under pressure through water pipe 206a and check valve 206b.Once water 206 enters ring pipe 201a, it continues through radial pipes201b, and finally passes through the spray nozzles 201c, where water 206becomes a mist spray. This spray of water then combines with theincoming cement 208, and is shown as dots at the center of the sprayhead assembly 201.

Admixture 207, which can be a liquid polymer acrylic, enters pipe 207athrough check valve 207b, and also flows through ring pipes 201a intoradial pipes 201b, and then through the spray nozzles 201c, where theadmixture combines with cement 208 to form a partial cementitiousmixture. Complete mixing occurs when this partially mixed cementitiousmixture enters the mixing assembly 202, where mixing occurs with theaction of the counter-rotating blades 202a. Control gate 202b regulatesthe flow of this completely-mixed cementitious material as it drops intothe mixing assembly 203, where it is caused to encapsulate aggregates 1through the action of the counter-rotating blades 203a. The optionalsecond coating sealant 7 is provided by increasing or decreasing thevolume of admixture 207 entering spray head 201.

It has been determined that the amount of admixture added to the water206 through the sprayhead assembly 201a does not affect the porosity ofthe mix design. The function of the admixture 207 is to produce thesealing and encapsulating qualities of the cementitious materials 6 and7.

This machine is intended to be suitable for with a range of materials,and preferably to be used to process materials of the types alreadydiscussed in connection with both the paving material and roadconstruction techniques already discussed. Thus, the machine itself isnot to be so limited, and it could nevertheless be used with other rawmaterials, and with other process conditions.

FIG. 6 shows pavement made from the recycled porous pavement which hasalready been described in connection with FIGS. 2 and 3. This embodimentdoes not have a predetermined internal structure, by which it is meantthat the layer of pavement is relatively homogenous. This is in contrastto formed structures having predetermined internal structures, whichstructures will be discussed hereinafter. Examples of such structuresinclude a porous aqueduct hollow core base and a porous rubberoverlayment friction course.

FIGS. 4A and 4B depict examples of environmental porous pavement 11which contains elements corresponding to those depicted in FIGS. 2 and3, as well as various other novel features of this invention. Suchpavement is preferably constructed in accordance with the materialrequirements just set forth. The pavement 11 has a porous hollowaqueduct core base 8, which base 8 is described in greater detailhereafter. The pavement is designed to provide for stormwater drainage.Although the pavement can be formed by a paving machine, such as thepaver which will be described, alternative methods of construction,including hand fabrication, could also be used. A solid state roll orsheet porous rubber overlayment 10 is placed atop the base 8, and thisoverlayment provides a friction course for the environmental porouspavement 11. Stormwater, whether from rain, melted snow or any othersource, can percolate through the overlayment via holes 10c to theenvironmental porous pavement 11. Overlayment 10 is discussed in greaterdetail below.

The core base 8 contains a number of aqueduct channels 9. As shown inFIGS. 4A and 4B, the aqueduct channels 9 are arch-shaped, but othershapes, such as round, square, rectangular, triangular, oval, crescent,semicircular, or arched, also could be used. Precipitation falling onthe porous road percolates as a liquid through the porous pavementmaterial and enters the aqueduct channels 9. Once inside the channels 9,the water can flow under the influence of gravity or, if necessary, canbe pumped.

The channels can be dimensioned and disposed so that they extenddownward to the sub-soil 5 underneath the core base 8; this way, waterentering the channels 9 can percolate directly downward into thesub-soil.

Although the embodiments of this invention are shown with elongatedchannels, other channel structures might be used. For example, shorterchannels not communicating with one another, much like the air cells ina sponge, could be used.

Among the benefits of using the integral porous hollow aqueduct corebase 8 is that it is no longer necessary to provide for storm drainagepipes and storm inlets of the type which are used to control water flowin conventional roads. Alternatively, such structures could be provided,although in reduced sizes.

A wide variety of conventional pavement construction techniques could beused with this aspect of the invention. For example, reinforcing rodscould be disposed among the pavement particles. Plastic coatedreinforcing rods, which are commercially available, and are thought tobe especially useful for this invention. The plastic coating would serveto limit the rust that occurs on unprotected rods.

By recycling existing polluting asphalt roads to form the pavementmaterials and structures shown in FIGS. 2-4A and 7, roads and parkinglots can be formed from recycled porous pavement material, and beconstructed with integral porous aqueduct hollow-core bases, wherebystormwater flooding can be greatly reduced. The porous pavement materialand aqueduct core roadbed together provide for improved stormwaterdrainage. A further benefit of this invention is that stormwater canpercolate through to the sub-base of the road bed, and so enter theground water aquifer. This reduces the amount and flow of water on thepavement surface, which decreases flooding.

FIG. 7 depicts the porous pavement with aqueducts 9 and other featuresalready discussed in connection with FIG. 4. It differs from FIG. 4 inthat it does not contain a porous rubber mat or sheet overlay.

Although the aqueduct core roadbed described above in connection withFIG. 4 is believed to be preferable, the porous pavement material alsocan be used to form a conventional road made from a relativelyhomogenous layer of material. As depicted in FIG. 6, the porous pavementmaterial can be applied in a conventional manner using conventionalpaving equipment. While the road shown in FIG. 6 will not have theability to provide longitudinal stormwater drainage in the manner of theembodiment shown in FIG. 4, it still will allow for vertical stormwaterpercolation to the sub-soil 5 below the road. Thus, the embodiment shownin FIG. 6 will also reduce skidding and hydroplaning.

As previously noted, many skidding accidents occur because water hasaccumulated on the road surface, in turn, leading to hydroplaning. Thisproblem is solved by the use of porous pavement, because standing wateris virtually eliminated from the road surface 11 of the porous pavement.Porous pavement therefore reduces conditions which would otherwise leadto skidding and hydroplaning. There are, moreover, a number ofadditional solutions to such drainage problems.

A further aspect of this invention involves the provision of a solidstate roll or sheet of a porous rubber overlayment material 10, which isshown in FIGS. 4A, 4B, 5 and 9A-C. This overlayment material 10 restsatop the road core 8, and serves as a friction course of the road bed11. Overlayment 10 can be held in place by a non-polluting adhesive,such as acrylic adhesive 14, preferably atop a recycled asphalt porouspavement structure course, as shown in FIGS. 4 and 5.

The solid state roll or sheet porous rubber overlayment friction course10 can be made from recycled rubber tire particles 10a which are bondedby a polymer binding component 10b. One example of an overlaymentfriction course 10 having this structure is shown in FIGS. 9A-C.

Particles falling within the range of 1/8"-1/4" (3-6 mm) are preferred.Examples of materials useful as binders include liquid polymers, such aspolyurethane, polyether and polyester, and these materials are availablefrom various rubber manufacturers and chemical companies.

EXAMPLE 5

One formula for the solid state roll or sheet porous rubber overlaymentfriction course 10 is as follows (the ratios given are volumetricratios):

one (1) part of polymer adhesion binder by volume; and

three (3) parts by volume of recycled rubber particles. Such particlescould be about 1/8"-1/4" (3-6 mm) in size. The distribution of particlesizes could be controlled at the recycling rubber tire plant where suchparticles are produced.

The solid state roll or sheet for the porous rubber friction course 10can be formed using a variety of known manufacturing processes, such asan extrusion process, compression molding process, injection moldingprocess, or casting process. These are all well-known manufacturingprocesses and so need not be described further herein. One materialbelieved to be particularly suitable for use in forming the porousrubber friction course 10 is the material PROLASTOMER®, which isproduced by the SYNTENE® company of Richmond Indiana. This material is athermoplastic rubber made from a polymer matrix and recycled rubber.

These processes use heat to form the finished product, with the amountof heat and other process conditions being selected according to thetype of equipment, the design mix formula, and the manufacturing processselected.

Although it is thought to be preferable to install the solid state rollor sheet porous rubber overlayment over the porous aqueduct hollow-corebase made of porous pavement, the overlayment also could be installedover conventional surfaces and road designs. FIG. 5 shows a solid stateroll or sheet porous rubber overlayment friction course 10 placed overan existing roadbed 18 made from a conventional asphalt or concretepavement material.

It is advantageous to be able to mount the overlayment friction course10, which is provided in the form of a porous solid state roll or matmade of porous rubber, over an existing roadbed friction course 18 madeof conventional asphalt or concrete pavement. This results in avirtually non-skid surface, and the porous rubber overlayment 10 can berapidly installed over an existing friction course made of conventionalasphalt or concrete pavement, that may be in need of repair. Thisprefabricated surface structure thereby allows for the rapid treatmentand/or repair of damaged road surfaces, such as the patching of potholesin existing roads. The speed with which repairs can be effected is ofparticular concern where there are heavy traffic conditions. Noelaborate paving equipment is required for overlayment of the sheet ormat. Unlike conventional asphalt pavement friction courses, whichrequire heating of the asphalt products being applied, the porous rubbersheet or mat can be laid at any temperature. Of course, it will beappreciated that moderate temperatures may be preferred, since theoverlayment material can be handled more easily at warmer temperatures.Finally, the porous rubber sheet or mat is a safer surface for vehicles,since as shown in FIG. 5, surface water is squeezed away from thevehicle tires, thereby reducing skidding and hydroplaning.

Another configuration of the porous or perforated overlayment frictioncourse 10 is shown in FIG. 9C with overlayment 10, containing grooves 9aon the underside that run the complete width of the overlayment 10. Itis seen in this configuration with a perforated overlayment 10. Theholes 10C intersect the grooves 9a so that rainwater entering the holeslOc passes into the grooves 9a. Since these grooves run transverse tothe road direction as shown in FIG. 9C, the water 9d will naturallydrain toward the sides of the road because the road structure slopes tothe side of the road. The depth and width of the grooves depend upon thethickness, t, of the overlayment 10. However, the maximum depth of thesegrooves could be one-half the thickness of t of the overlayment. Thecenterline to centerline distance would be 2t, 3t, 4t etc. dependingupon the anticipated average or maximum rain intensity.

A further benefit to the use of the grooved overlayment 10 is that theoverlayment can be formed with grooves which will contain wiring,whether electrical or fiberoptic, for road sensors and/or controlsystems. For example, traffic sensors embedded in the roadway could belinked to a computer, and the computer linked to traffic signals, viawiring running beneath the overlayment. Such grooves can be formed inthe overlayment either by machining the finished overlayment, or bymanufacturing the overlayment in an extrusion process which forms thegrooves.

It also will be appreciated that this aspect of the grooved overlaymentis particularly useful for the implementation of "smart" roads, in whichvehicles will be operated under automatic control. Automatic operationwill require a substantial number of sensors and control systems, and itwill be simpler to place such sensors and systems beneath theoverlayment than to place them into trenches cut in the pavement itself.

Another advantage of this friction course 10 is that it can be made frompost-consumer recycled (rubber tires) and so will have a molecularstructure similar to the structure of the vehicle tires rolling on it.This combination of similar materials produces optimal conditionsbraking a vehicle, since the coefficient of friction between the likesurfaces is maximized.

Another benefit to using the friction overlayment is that it offers ahigh coefficient of friction. A high cost of friction, of course, meansimproved vehicle handling. In contrast, conventional asphalt andconcrete roads are composed of stone aggregates and sand, which becomepolished by vehicle traffic, reducing the coefficient of brakingfriction between the tire and the roadbed. In the case of the asphaltroad, which contains oils, those oils further reduce the coefficient ofbraking friction between tires and the roadbed, because the oils act aslubricants, reducing the coefficient of friction.

An alternate configuration for the solid state roll or sheet porousrubber overlayment friction course 10 is to form the overlayment insolid sheets and later perforate the sheet with numerous holes lOc,either on or off the construction site. The porosity of the perforatedsheets can thereby be made similar to that of the porous rubber mat 10,previously described.

Perforation process for forming perforated rubber sheets are known, andso need not be described in further detail herein.

The perforations can be made with various diameters and be disposed invarious patterns. For example, typical hole sizes could range from1/16"-1/4" (1.58 mm-6.35 mm). In any event, the optimal patterns andhole sizes can be determined for any given installation on an individualbasis through suitable testing. The spacing of these perforated holescan vary, depending upon the diameter of perforations. The spacing ofthese perforations can be made multiples of the diameter of theperforations, such as 3×, 4×, 5× the perforation diameter. The precisespacing used can depend upon the desired rate of water percolation.Examples of the hole distribution patterns include random spacing andregularly-spaced rows and columns. It is contemplated that all possiblepatterns and opening sizes fall within the scope of this invention.

Another option would be not to provide any perforations. Thisarrangement might be preferable in areas that are normally well-drainedwith catch basins and pavement slopes, where it is more important forthe road to have a high coefficient of friction to allow more effectivevehicle braking, and also to minimize conditions that produce pot-holes.Using a solid-state roll or sheet rubber overlayment friction coursewould be ideal in such conditions, say, at a corner in Times Square, inNew York City, or at approaches to toll booths, such as entrances to abridge.

Future roads can also be improved by sending heated air or other fluidthrough the aqueducts 9, to melt ice and snow which has accumulated onthe road surface 11. Beyond the immediate improvement in safety, theneed for snow removal equipment can be minimized, or possibly eveneliminated. Thus, another aspect of this invention is an all-weathersystem which facilitates driving during winter months, when snow and icewould otherwise result in hazardous driving conditions.

This invention also involves a paving machine which can form theaforementioned aqueduct road core structure. As shown in FIGS. 8A-D,such a machine can be constructed by modifying conventional pavingequipment. A wide variety of paving machines and related devices areknown, and examples of such paving machines can be found inmanufacturer's industrial catalogs. This embodiment of the presentinvention involves modifying a conventional paving machine materialhopper to include a mixer 101 which forms the porous pavement particles.The mixer 101 consists of a pair of elongated, counter-rotating, mixingblades 103.

The mixer 101 is used to produce a homogeneous mixture of asphalt,preferably recycled, in the manner discussed previously in thisapplication. The mixing blades 103 also maintain the flowability of thepaving particles.

Process conditions and starting materials are preferably selected in thesame fashion as those previously discussed in connection with thepavement materials according to this invention, as well as thosedescribed hereinafter. In particular, such conditions are discussed indetail in connection with the explanation of the mixing machineaccording to this invention.

The mixed pavement particles are applied atop the sub-soil 105 using apaving machine of the type shown in FIGS. 8A-D. Some of the componentsof this paving machine are conventional paving machine components (i.e.,chassis, conveyor and pumping equipment for feeding paving material fromthe hopper to the screed), and these components serve to feed theparticles to a specially-designed screed 107. As seen in FIGS. 8A-D,screed 107 has a number of substantially-parallel, regularly spacedaqueduct forming rods 109 attached thereto. These rods, which areoriented along the axis of movement of the paving machine, serve to formthe aqueduct shape 9 in the base 8 of the road, which as previouslynoted is made of porous pavement.

The pavement is formed by continuously depositing a mass of pavementparticles onto the forming rods 109 as the paving machine moves forward.The forming rods thereby serve to create elongated aqueduct cores underthe road surface. In addition, it may be desirable to form the formingrods 109 with a taper so that they narrow away from the screed. Formingrods 109 may be rotated and/or heated, in order to improve release ofthe pavement material as the paving machine advances.

Optionally, a leveling roller 111 rides atop the pavement near the endof the forming rods. The leveling roller 111 extends over the completewidth of the pavement being formed, and bears downward against thepavement surface to produce a smooth finish, insure the required amountof pavement material compaction, and cause the aqueduct core to have theproper shape.

The downward force can be applied with hydraulic pistons or bymechanical linkage and spring means. Such pressure causes the roller tosmooth out and level top aggregates that may become loose in the pavingprocess. The appropriate amount of pressure is determined visually, byinspecting the quality of the top finish. Any necessary adjustments canbe made to produce the optimum finish.

In addition, a system for applying coating liquid to the pavementmaterial is provided (that is, an applying means for applying a treatingagent). As shown in FIG. 8A, this system uses fogging spray nozzles 113located beyond (behind) the roller 111 to coat the finished pavementwith a fog or mist spray of curing compound 114. The curing compound iscarried via delivery pipes 112 from a curing compound reservoir 115through the action of dispensing pump 116. The fogging spray nozzlesthereby serve to coat the finished pavement with curing compound.

The curing compound, which is withdrawn from the reservoir 115 andforced through the nozzle 113 under pressure by the dispensing pump 116,emerges as a spray, and this spray can be adjusted at either the nozzleand/or the pump to ensure a fine mist spray.

The quantity of curing compound may be adjusted so that the top layer ofthe pavement does not become overloaded, which would produce animpervious surface, and the preferred amount and size of the mist can bedetermined empirically.

The curing compound serves to control and reduce the evaporation rate ofthe pavement material using its hydration or curing process. There aremany commercially available curing compounds available on the market.They are basically liquid plastics such as liquid acrylics, liquid latexand other polymers.

Other variations and modifications of this invention will be apparent tothose skilled in this art after careful study of this application. Thisinvention is not to be limited, whether by materials, constructionsand/or procedures, save as set forth in the following claims.

What we claim is:
 1. A paving machine for forming a pavement on asubsurface from a pavement material as said paving machine moves along adirection of travel, comprising:a mixing unit comprising a hopper and atleast a pair of mixing rolls disposed therein for processing of thepavement material; a screed for depositing the pavement material ontothe subsurface, said screed comprising a plurality of elongated formingarms each having a cross-sectional shape and which said elongatedforming arms are approximately parallel to one another, and to thedirection of travel, said screed depositing the pavement material ontothe arms so that as said paving machine moves in the direction oftravel, the pavement is formed with a plurality of channels therein; andconveying means for conveying the pavement material from said mixingunit to said screed.
 2. A paving machine as in claim 1, wherein at leastsome of said cross-sectional shapes are arch-shaped.
 3. A paving machineas in claim 1, wherein at least some of said cross-sectional shapes areround.
 4. A paving machine as in claim 1, wherein at least some of saidforming arms are tapered.
 5. A paving machine as in claim 1, wherein atleast some of said forming arms rotate about a rotation axis which isapproximately parallel to the direction of travel.
 6. A paving machineas in claim 1, further comprising a smoothing roll located by saidscreed, said smoothing roll having a roll axis which is approximatelyperpendicular to the direction of travel.
 7. A paving machine as inclaim 1, further comprising applying means for applying a treating agentto the pavement material.
 8. A paving machine as in claim 7, where saidapplying means comprises:a reservoir for containing the treating agent;at least one nozzle through which the treating agent is applied to thepavement material; and a pump which feeds the treating agent from thereservoir to the nozzle.